Just lol at the idea that you won't run into borrow checker issues when dealing with strings though.
I think what's being called "trivial" is doing a bit of regex searching. It's probably accurate to call that trivial for an experienced Rust programmer, but if you're just beginning, I don't think it's helpful to call anything trivial. I still remember my first exposure to Rust. It was different. It took a bit to grok. But once it clicked, things were much better.
As the maintainer of the regex crate, I invite you or anyone to ask for help using regexes. The regex repo has Discussions opened up, so it's appropriate to ask for help, even if they are beginner questions: https://github.com/rust-lang/regex/discussions
As usual though, try to provide as many details as you can. Giving the source code you have but can't get to work is a great start, for example.
https://doc.rust-lang.org/rust-by-example/ and https://github.com/rust-lang/rustlings might be good places to visit to gain that experience, as well as improving the specific diagnostics to be more actionable.
Yes, I figured that to be the case, but still wanted to say, "Discussions are open for questions, even if they are beginner related, as long as it's related to regex'ing somehow." :-)
https://play.rust-lang.org/?version=stable&mode=debug&editio...
https://github.com/danielzfranklin/drm-fourcc-rs/blob/main/b...
https://play.rust-lang.org/?version=stable&edition=2018&gist...
But what you really want is to get your head around ownership and borrowing, especially when it comes to the scoped RAII that rust has (e.g. freeing a String while a reference to it still exists and is being used would give you the "temporary value dropped while borrowed" error).
Just do the first regex search, then escape into a String with regex::escape, then build a regex from the String and search with it.
Of course what you are doing is probably wrong since you should use a string matching crate rather than escaping characters and using a regex matching crate.